3,451 research outputs found
On the stability of homogeneous solutions to some aggregation models
Vasculogenesis, i.e. self-assembly of endothelial cells leading to capillary network formation, has been the object of many experimental investigations in recent years, due to its relevance both in physiological and in pathological conditions. We performed a detailed linear stability analysis of two models of in vitro vasculogenesis, with the aim of checking their potential for structure formation starting from initial data representing a continuum cell monolayer. The first model turns out to be unstable at low cell densities, while pressure stabilizes it at high densities. The second model is instead stable at low cell densities. Detailed information about the instability regions and the structure of the critical wave numbers are obtained in several interesting limiting cases. We expect that altogether, this information will be useful for further comparisons of the two models with experiments
Molecular Dynamics Simulation of Vascular Network Formation
Endothelial cells are responsible for the formation of the capillary blood
vessel network. We describe a system of endothelial cells by means of
two-dimensional molecular dynamics simulations of point-like particles. Cells'
motion is governed by the gradient of the concentration of a chemical substance
that they produce (chemotaxis). The typical time of degradation of the chemical
substance introduces a characteristic length in the system. We show that
point-like model cells form network resembling structures tuned by this
characteristic length, before collapsing altogether. Successively, we improve
the non-realistic point-like model cells by introducing an isotropic strong
repulsive force between them and a velocity dependent force mimicking the
observed peculiarity of endothelial cells to preserve the direction of their
motion (persistence). This more realistic model does not show a clear network
formation. We ascribe this partial fault in reproducing the experiments to the
static geometry of our model cells that, in reality, change their shapes by
elongating toward neighboring cells.Comment: 10 pages, 3 figures, 2 of which composite with 8 pictures each.
Accepted on J.Stat.Mech. (2009). Appeared at the poster session of
StatPhys23, Genoa, Italy, July 13 (2007
Vascular networks due to dynamically arrested crystalline ordering of elongated cells
Recent experimental and theoretical studies suggest that crystallization and
glass-like solidification are useful analogies for understanding cell ordering
in confluent biological tissues. It remains unexplored how cellular ordering
contributes to pattern formation during morphogenesis. With a computational
model we show that a system of elongated, cohering biological cells can get
dynamically arrested in a network pattern. Our model provides a new explanation
for the formation of cellular networks in culture systems that exclude
intercellular interaction via chemotaxis or mechanical traction.Comment: 11 pages, 4 figures. Published as: Palm and Merks (2013) Physical
Review E 87, 012725. The present version includes a correction in the
calculation of the nematic order parameter. Erratum submitted to PRE on Jun
5th 2013. The correction does not affect the conclusion
Interactions between endothelial cells and HIV-1.
Endothelial cells (EC) participate in inflammatory and immune reactions by producing and responding to soluble mediators. Human immunodeficiency virus (HIV)-1 profoundly alters the features of EC. In some anatomical districts, they are infected by the virus and may represent a relevant reservoir. During lymphomononuclear cell diapedesis, EC activate virus replication in crossing cells. Direct or indirect damage of EC is particularly relevant in central nervous system, where blood-brain barrier perturbation is pivotal in neuronal degeneration. The observed alterations of EC adhesive properties contribute in altered leukocyte traffic from blood to lymphoid organs and tissues and play a role in the onset of immune surveillance alteration. These alterations of EC functions are relevant for the general vasculopathy, which marks the acquired immunodeficiency syndrome, and in particular are instrumental in the pathogenesis of Kaposi's sarcoma. Here we discuss the biological and molecular activation of EC in HIV-1 infection that represents the basis to understand the pathogenesis of HIV-1 associated vascular diseases
Modelling the motion of a cell population in the extracellular matrix
The paper aims at describing the motion of cells in fibrous tissues taking into account of the interaction with the network fibers and among cells, of chemotaxis, and of contact guidance from network fibers. Both a kinetic model and its continuum limit are described
Modeling cell movement in anisotropic and heterogeneous network tissues
Cell motion and interaction with the extracellular matrix is studied deriving a kinetic model and considering its diffusive limit. The model takes into account of chemotactic and haptotactic effects, and obtains friction as a result of the interactions between cells and between cells and the fibrous environment. The evolution depends on the fibre distribution, as cells preferentially move along the fibre direction and tend to cleave and remodel the extracellular matrix when their direction of motion is not aligned with the fibre direction. Simulations are performed to describe the behavior of ensemble of cells under the action of a chemotactic field and in presence of heterogeneous and anisotropic fibre networks
Hybrid inorganic/organic photonic crystal biochips for cancer biomarkers detection
We report on hybrid inorganic/organic one-dimensional photonic crystal biochips sustaining Bloch surface waves. The biochips were used, together with an optical platform operating in a label-free and fluorescence configuration simultaneously, to detect the cancer biomarker Angiopoietin 2 in a protein base buffer. The hybrid photonic crystals embed in their geometry a thin functionalization poly-acrylic acid layer deposited by plasma polymerization, which is used to immobilize a monoclonal antibody for highly specific biological recognition. The fluorescence operation mode is described in detail, putting into evidence the role of field enhancement and localization at the photonic crystal surface in the shaping and intensification of the angular fluorescence pattern. In the fluorescence operation mode, the hybrid biochips can attain the limit of detection 6 ng/ml.We report on hybrid inorganic/organic one-dimensional photonic crystal biochips sustaining Bloch surface waves. The biochips were used, together with an optical platform operating in a label-free and fluorescence configuration simultaneously, to detect the cancer biomarker Angiopoietin 2 in a protein base buffer. The hybrid photonic crystals embed in their geometry a thin functionalization poly-acrylic acid layer deposited by plasma polymerization, which is used to immobilize a monoclonal antibody for highly specific biological recognition. The fluorescence operation mode is described in detail, putting into evidence the role of field enhancement and localization at the photonic crystal surface in the shaping and intensification of the angular fluorescence pattern. In the fluorescence operation mode, the hybrid biochips can attain the limit of detection 6 ng/ml
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